Extending Planar Orientation Control Range of Grasped Objects Using Selective Actuation in a Redundant Parallel-Driven Soft Gripper
Abstract
Soft grippers enable stable grasping through compliant structures and multipoint contact; however, manipulating the pose of a grasped object while maintaining contact remains challenging, particularly when large pose changes are required. Conventional approaches based on locally estimated drive matrices are limited to small motions owing to the actuator stroke and approximation validity. This study proposes a selective actuation strategy for redundant parallel-driven soft grippers to generate large object pose changes through the iterative application of small motions. By exploiting actuation redundancy, predefined actuator groups that satisfy the force-closure conditions are alternately activated. The partial drive matrices corresponding to each actuator group are extracted from a single, globally estimated drive matrix, enabling the discrete switching of control inputs without re-estimation. After reaching the vicinity of the target pose, the control scheme is switched to a full-actuator configuration for high-precision position and orientation regulation. Experiments using a fabricated redundant soft gripper demonstrated that large pose changes, which are difficult to achieve with a single control action, can be realized step-by-step while maintaining stable grasping.